Field of Invention
This invention relates to a novel mutation in a sorghum gene which increases the seed yield in sorghum. The amino acid sequence of this mutated gene and its encoded protein are included. This invention also relates to genetically altered plants having this mutated gene and/or containing the mutated protein and which have increased flower production and seed yield.
Description of the Prior Art
Grain yield is determined by the number of plants per acre, seed number per plant (also called “seed yield”), and seed weight. Among all these yield components, seed number per plant is a major determinant of grain yield in sorghum [Sorghum bicolor (L.) Moech] and other cereal crops (Saeed, et al., Crop Sci. 26:346-351 (1986); Duggan, et al., Can. J. Plant Sci. 80:739-745 (2000); Richards, J. Exp. Bot. 51:447-458 (2000); Ashikari, et al., Science 309:741-745 (2005); Reynolds, et al., J. Exp. Bot. 60:1899-1918 (2009)). Increased seed number and seed size, which are directly related to improved grain yield, were common goals during domestication of cereal crops resulting in inadvertent selection of genetic stocks with greater seed number and larger seeds (Zohary, et al., Domestication of Plants in the Old World: The Origin and Spread of Cultivated Plants in West Asia. Europe, and the Mediterranean Basin. 4 ed. Oxford University Press, Oxford, U.K. (2012)).
Seed number per panicle is determined by several attributes of the inflorescence, including the number and length of the primary and secondary flower branches, and fertility of spikelets. In sorghum, the inflorescence or panicle has a main rachis on which many primary branches are developed. Secondary branches and sometimes tertiary branches develop from the secondary branches (Brown, et al., Theor. Appl. Genet. 113:931-942 (2006); Burow, et al., Crop Sci. 54:2030-2037 (2014)). The main inflorescence, primary branches, secondary branches, and tertiary branches all end with a terminal triplet of spikelets, which consist of one sessile bisexual spikelet and two lateral staminate pedicellate spikelets (Walters and Keil, Vascular Plant Taxonomy. 4th ed. Kendall/Hunt Pub. Co., Dubuque, Iowa, USA (1988)). Below the terminal spikelets, one or more spikelet pair can develop, and these adjacent spikelet pairs consist of one sessile and one pedicellate spikelet. In the wild-type sorghum line BTx623 and all other characterized natural sorghum accessions, only the sessile spikelets are perfect flowers and can develop into seeds. The development of pedicellate spikelets is arrested at various stages in different sorghum lines. In some lines, the pedicellate spikelets can develop anthers and shed viable pollen, but few lines can develop ovary and produce viable seeds (Karper and Stephens, J. Hered. 27:183-194 (1936)). Thus, the pedicellate spikelets in the wild type eventually abort.
Recently, a novel group of sorghum mutants were generated by subjecting sorghum seeds to ethyl methane sulfonate (EMS). The seeds were grown and back-crossed with wild-type sorghum line BTx623 and the seeds from those crosses were germinated. Many of the mutated sorghum plants were isolated and characterized. These sorghum mutants were designated as multiseeded (msd) mutants because the developmental arrest of the pedicellate spikelets was released (Burow, et al. (2014)). See also U.S. Patent App. Publication No. 2014-0068798. While all of these mutated sorghum mutants had increased seed count, they exhibited different and distinctive phenotypes. Only recently has one genetic mutation which results in one of the distinctive phenotypes been characterized. This msd1 gene and its distinctive phenotype is the subject matter of U.S. Patent App. 62/132,574 filed on Mar. 13, 2015. Through next-generation sequencing of the pooled genomic DNA of homozygous mutants selected from a backcrossed F2 population derived from a cross of msd1-1 (p12) to BTx623, the MSD1 gene has been identified as a TCP-domain plant-specific transcription factor.
The genetic mutations in another set of sorghum plants with an interesting MSD phenotype are investigated, and the mutations that give rise to the identified phenotype are described herein, along with a description of the phenotype.